As the U.S. bond rating falls and the stock market plunges, the American Century looks to be well and truly over. While this has provoked no small amount of hand-wringing, Americans may soon come to enjoy no longer bearing the responsibility for running the world's indispensable nation.

The signs of decline are everywhere. Illegal immigrants are heading back home in search of a better life. China already leads the world in green technology and is about to become the world's biggest economy in terms of purchasing power. Two U.S.-led wars are dragging toward an end charitably described as: mission not completely failed. The United States was able to avoid default only by stopping pretty much all other government business for several weeks. And it's not only U.S. political and economic preeminence that is deteriorating, but its cultural hegemony: India's Bollywood and Nigeria's Nollywood are each producing more films a year than Hollywood (to say nothing of their superior artistic quality).

Of course, the United States still possesses greater military strength than any other country in the world. But what good has being the world's policeman done for Americans? Wielding that might meant the United States saw more combat deaths overseas last year than any other country, according to data from Uppsala University. Beyond the blood is the treasure: U.S. military spending increased 81 percent between 2001 and 2010 and now accounts for 43 percent of the global total -- six times its nearest rival, China. The U.S. military burden is equivalent to 4.8 percent of GDP, the largest economic burden of any OECD country.

It is no coincidence that the man who coined the term "imperial overstretch," Yale University historian Paul Kennedy, is British. Britain was the last country to get knocked off the top spot, after all -- and the United States could learn a lot from its experience.

Britain spent much of the 1950s pretending it was still a global power, which resulted in one of the country's grimmest decades -- food was still rationed until 1954. This exercise in delusion culminated in Britain's attempt to occupy the Suez Canal in 1957, an effort that was scuttled by the world's new ascendant power, the United States.

But it was only a year after the Suez crisis signaled the end of Britain's global reach that British Prime Minister Harold Macmillan declared his compatriots "never had it so good." He was right: Average incomes, health indicators, and levels of education were all far better than in the glory days when Britannia ruled the seas. Then, after Britain gave up on empire -- decolonizing across Africa and Asia in the early 1960s -- they got the Beatles, the Mini, and free love.

Britain may still go on about "punching above its weight" in international affairs, and it has kept some of the trappings of great-power status, such as a seat on the U.N. Security Council and a small flotilla of nuclear submarines, but its burdens are significantly less momentous. Freed from the distractions of colonial oversight and global leadership, it could retire its planet-spanning chain of military bases, shrink the Royal Navy, and devalue the pound without fears that the world would come to an end. And the country learned to collaborate without feeling equal status was a slight to its dignity -- joining the European Union, for example, and signing the Kyoto Protocol.

Could the United States go down the same track toward contented (well, most of the time), pretty-good-power status? The British experience suggests that the first step is to accept you have a problem. The simple fact that Britain couldn't afford to keep its empire together after World War II helped forge that acceptance -- and it might resonate in the United States at the moment.

Perhaps Washington could take a baby step or two toward scaling back its global commitments by returning the defense budget to its Reagan-era average, a move that would save about $250 billion a year. Surely what was good enough for a world riven by the Cold War, when the Warsaw Pact had 249 combat divisions and we lived in constant threat of global thermonuclear Armageddon, is also good enough for the United States today -- at a time when al Qaeda apparently has fewer than 100 fighters left in Afghanistan. And it really would be a baby step: Even with a $250 billion cut, the United States would still outspend China about four times over.

Defense cuts would allow the United States to tend to a few other priorities, which just might take Americans' minds off the fact that their country is no longer No. 1. Perhaps the United States could focus on constructing a high-speed rail line or two, or maybe even finish the job on extending health care. After all, of the large economies that enjoyed a AAA rating from Standard & Poor's last week, the United States ranked at the bottom of the list in terms of life expectancy, and it was the only country without universal health care. Perhaps America could also spend a little more on basic education; the United States was at the tail end of the AAA club when it came to believing basic scientific truths like evolution, and it scored lowest out of all those countries on international tests of students' math skills.

The end of Britain's imperial ambitions allowed the country to abandon national service and just relax a little. Similarly, with less need to flag the martial spirit through adrenaline-pumping threat alerts and wars on terror, the United States could find a moment to reform its criminal justice system; another international indicator where the United States remains in the lead, after all, is in percentage of its population behind bars. And once America accepts it doesn't need to work every waking hour to keep up with the Soviets, Japanese, or Chinese, perhaps it could take time for a vacation. At the moment, there is no statutory minimum for paid leave in the United States. Even Singapore provides seven days, and the rest of the AAA club gives employees minimums ranging from 18 to 30 days.

As to foreign relations, the United States couldn't -- and wouldn't -- follow Britain's example and join the European Union, but here too, there could be scope for baby steps. What about signing up for the International Criminal Court or taking a less obstructive line during climate negotiations? In fact, a decline from hyperpower status will doubtless help prolong the upward trend in international opinion of the United States. It's even possible that the U.S. government could get more done in the world by playing nice than barging around on its own.

Whatever happens to the United States in the global economic rankings, it will remain a great country. Accepting -- even embracing -- decline will serve as a reminder that American exceptionalism is built on a set of values, not stock indices. If the S&P downgrade helps the United States foster a shift toward prioritizing the good life over great-power status, perhaps it will be seen as a blessing in disguise. What's more, the United States starts out its decline with many advantages over 1950s Britain. Not least, in large parts of the country, it is already possible to find a good restaurant -- something that took the Brits 30-plus years of not-so-bad power status to achieve.